Most semiconductor devices are made on silicon, and the starter substrate for any circuit is a silicon wafer, typically 6, 8 or 12 inch in diameter. Wafers are sliced from large single-crystal silicon ingots and polished to extreme tolerances. Ingots are usually made using a method called CZ (short for its inventor, the Polish scientist Jan Czochralski, who pioneered single crystal growth of metals from 1916). During this process, high purity polysilicon chunks are melted in a quartz crucible, a single crystal seed of silicon is lowered to just touch the melt and drawn up slowly. At the end of the process, a large single-crystal ingot has grown, replicating the structure of the seed.
Single crystal silicon wafers are the basis of integrated circuits or discrete electronic components such as transistors and diodes. After the CZ growth of the silicon ingot, which today can exceed 12 in./300 mm in diameter and several feet in length, there are seven steps in wafer manufacturing. Innovative Organics provides coolants, lubricants, abrasive slurries and cleaners for all of the wafer manufacturing steps.
Seven Steps in Wafer Manufacturing
| Step 1: | Grinding: “Top and Tail Grind” to remove ingot end profiles and provide flat ends; OD/Cylindrical Grind to generate a perfect, cylindrical ingot; Orientation Flat Grind to provide a true crystallographic plane reference flat(s).
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| Step 2: | Sawing/Wafering: Large diameter ingots are sliced using a wire saw that uses silicon carbide abrasive slurry, whereas smaller diameter ingots, 6” and less are wafered using an ID saw (a steel “doughnut” shaped blade with an ID edge electroplated with diamond abrasive).
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| Step 3: | Edge Grinding: Wafers are edge ground to provide a chamfered or beveled edge profile. This precaution helps to minimize edge damage to the wafers during subsequent process steps.
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| Step 4: | Lapping: Both faces of the wafers are lapped with abrasive slurry to remove surface and sub-surface damage induced during the wafering step.
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| Step 5: | Etching: The wafers are immersed in an acid etch to remove surface and sub-surface damage generated during lapping.
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| Step 6: | Polishing: One or both faces of the wafers are polished with colloidal silica slurry to a “mirror” finish exhibiting zero defects.
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| Step 7: | Cleaning (In – Process & Final) : The wafers are cleaned between the previous process steps and then receive a final clean to remove residual process detritus and trace deposits of wafer mounting wax.
Wafer Thinning: After devices are fabricated onto a silicon wafer, the reverse wafer face must be ground, lapped or polished. As a relatively thick wafer is fabricated to increase device yields, it becomes necessary to reduce the wafer's thermal mass by these critical thinning processes. Also, the thinning process should not generate excessive surface or sub-surface damage in the fabricated wafer, as this will impair the electrical performance of the devices. Special attention must be given to the optimum choice of abrasives and machining fluids because of the high cost of the fabricated wafer.
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Choose from the following products for the Semiconductor market.
Abrasive Slurries Cleaners Coolants Lapping Vehicles | Polishing Pads Polishing Slurries / Particles Specialty Fluids / Other Wire Slicing Vehicles |